Centre Number
Candidate Number
Name
UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS
General Certificate of Education Ordinary Level
5070/03
CHEMISTRY
Paper 3 Practical Test
May/June 2006
1 hour 30 minutes
Candidates answer on the Question Paper.
Additional Materials: As listed in the Instructions to Supervisors.
READ THESE INSTRUCTIONS FIRST
Write your Centre number, candidate number and name in the spaces at the top of this page.
Write in dark blue or black pen in the spaces provided on the Question Paper.
You may use a pencil for any diagrams, graphs or rough work.
Do not use staples, paper clips, highlighters, glue or correction fluid.
You may use a calculator.
Answer all questions.
The number of marks is given in brackets [ ] at the end of each question or part question.
Qualitative analysis notes are printed on page 8.
You should show the essential steps in any calculation and record experimental results in the spaces
provided on the question paper.
For Examiner’s Use
1
2
TOTAL
This document consists of 7 printed pages and 1 blank page.
SP (SJF3664) T11209/2
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2
1
Compound X is an oxidising agent. An acidified solution of X oxidises potassium iodide to
iodine which can be titrated with sodium thiosulphate.
Solution P was prepared by dissolving 1.70 g of compound X in 1.00 dm3 of distilled water.
You are to determine the relative molecular mass of X.
Solution Q is 0.100 mol/dm3 sodium thiosulphate, Na2S2O3.
(a) Fill the burette with solution Q.
Pipette a 25.0 cm3 (or 20.0 cm3) portion of P into a flask and add about a test-tubeful of
dilute sulphuric acid followed by about a test-tubeful of aqueous potassium iodide. The
solution should turn red-brown. Do not add the starch indicator at this stage.
Add Q from the burette until the red-brown colour fades to pale yellow, then add a few
drops of the starch indicator. This will give a dark blue solution. Continue adding Q
slowly from the burette until one drop of Q causes the blue colour to disappear, leaving
a colourless solution. Record your results in the table, repeating the titration as many
times as you consider necessary to achieve consistent results.
Results
Burette readings
titration number
1
2
final reading / cm3
initial reading / cm3
volume of Q used / cm3
best titration results (✓)
Summary
Tick (✓) the best titration results.
Using these results, the average volume of Q required was ………… cm3.
Volume of P used was ………… cm3.
[12]
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For
Examiner’s
Use
For
Examiner’s
Use
3
(b) Q is 0.100 mol/dm3 sodium thiosulphate.
One mole of X reacts with potassium iodide to produce iodine. The iodine produced
reacts with two moles of sodium thiosulphate.
Calculate the concentration, in mol/dm3, of X in solution P.
Concentration of X in solution P is ……………………………… mol/dm3.
[2]
(c) P contains 1.70 g/dm3 X.
Using your answer to (b), calculate the relative molecular mass of X.
Relative molecular mass of X is ………………………………
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[2]
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4
2
You are provided with solid R and solution S both of which contain a compound of the same
transition metal. Carry out the following experiments and record your observations in the
table. You should test and name any gas evolved.
Tests on solid R
test
no.
observations
test
1
Add a portion of aqueous hydrogen
peroxide to a small sample of R.
2
Add 1-2 cm3 of concentrated
hydrochloric acid to a sample of R and
warm gently.
[9]
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For
Examiner’s
Use
For
Examiner’s
Use
5
Tests on solution S
test
no.
3
test
observations
(a) To a portion of S, add aqueous
sodium hydroxide until a change is
seen.
(b) Add excess aqueous sodium
hydroxide to the mixture from (a)
and allow to stand for a few
minutes, shaking occasionally.
(c) To a portion of the mixture from (b),
add a few drops of aqueous
hydrogen peroxide.
4
(a) To a portion of S, add an equal
volume of aqueous silver nitrate.
(b) Add dilute nitric acid to the mixture
from (a).
5
(a) To a portion of S, add an equal
volume of aqueous barium nitrate.
(b) Add dilute nitric acid to the mixture
from (a).
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For
Examiner’s
Use
6
test
no.
6
test
observations
To a portion of acidified potassium
manganate(VII), add an equal volume of
solution S.
[12]
Conclusions
In test 1, solid R is acting as …………………………………
In test 2, solid R is acting as …………………………………
The anion (negative ion) present in solution S is …………………………………
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[3]
7
BLANK PAGE
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8
NOTES FOR USE IN QUALITATIVE ANALYSIS
Tests for anions
test
test result
add dilute acid
effervescence, carbon dioxide
produced
chloride (Cl –)
[in solution]
acidify with dilute nitric acid, then add
aqueous silver nitrate
white ppt.
iodide (I –)
[in solution]
acidify with dilute nitric acid, then add
aqueous lead(II) nitrate
yellow ppt.
nitrate (NO–3)
[in solution]
add aqueous sodium hydroxide then
aluminium foil; warm carefully
ammonia produced
sulphate (SO24–)
[in solution]
acidify with dilute nitric acid, then add
aqueous barium nitrate
white ppt.
anion
carbonate
–
(CO23 )
Tests for aqueous cations
cation
effect of aqueous sodium hydroxide
effect of aqueous ammonia
aluminium (Al 3+)
white ppt., soluble in excess giving a
colourless solution
white ppt., insoluble in excess
ammonia produced on warming
–
white ppt., insoluble in excess
no ppt. or very slight white ppt.
light blue ppt., insoluble in excess
light blue ppt., soluble in excess giving
a dark blue solution
+
iron(II) (Fe2 )
green ppt., insoluble in excess
green ppt., insoluble in excess
iron(III) (Fe3+)
red-brown ppt., insoluble in excess
red-brown ppt., insoluble in excess
white ppt., soluble in excess giving a
colourless solution
white ppt., soluble in excess giving a
colourless solution
+
ammonium (NH4 )
2+
calcium (Ca )
copper(II)
(Cu2+)
2+
zinc (Zn )
Tests for gases
gas
test and test result
ammonia (NH3)
turns damp red litmus paper blue
carbon dioxide (CO2)
turns limewater milky
chlorine (Cl 2)
bleaches damp litmus paper
hydrogen (H2)
“pops” with a lighted splint
oxygen (O2)
relights a glowing splint
sulphur dioxide (SO2)
turns aqueous potassium dichromate(VI) from orange to green
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